LANBased.0f802.11and.ItsDeVel0Pment802-11WirelessLocalAreaNetworkanditsDevelopmentDengDa,SoftwareandTheoryProfessional,SchoolofComputerSchool,UniversityofElectronicScienceandTechnologyAbsractIhetecllnlaueOtWL-AN( WireIessLocalAreaNet'work)lsde-veIOpingrapIdIytheseyears,andltsap-pIlcationlssprea( jingineverywalk0flifeThIsarticlemakesabriefintr0ductlon0fWLAN})asecIOf80211Dr0tocolln3aspec:ts:developmenI.princIple, andItsse(: urltv In recent years, wireless LANs have gained widespread adoption and significant growth.
Today's domestic, education and research, health care and other fields and manufacturing, warehousing and other industries are widely used wireless networks.
More and more companies, enterprises to improve competitiveness, are scrambling to adopt wireless networks to facilitate mobility network access. Improve work efficiency . Reduce long-term investment costs.
First, the concept of wireless LAN wireless network is the use of electromagnetic waves in the air to send and receive data, without the need for cable media connection form of network.
It is a complementary and expansion of the wired network, so that computers on the Internet with mobility. Can quickly and easily solve the problem of network connectivity that is not easily achieved using wired methods.
With the popularity of personal wireless mobile devices, the traditional wired network in some cases difficult to meet the requirements of the mobile office.
The wireless network has the unparalleled advantages of a traditional wired network (1) Flexibility.
In a wired network, the placement of network equipment is limited by the location of the network and geographic location. And wireless LAN as long as the wireless signal coverage area, any location can access the network.
Another advantage of wireless LANs is their mobility. Users connected to a wireless LAN can move anywhere within the signal coverage area and remain connected to the network at the same time.
(2) Easy to install.
Wireless LAN can eliminate or minimize the workload of network wiring, generally as long as the installation of one or several access point devices, you can establish a local area network covering the entire region.
(3) Easy to maintain.
Wired network if there is a network failure due to poor line connections. It is often difficult to check and it costs a lot to overhaul the lines.
Wireless networks are easy to locate the fault. Simply replace the device to restore the network connection.
(4) easy to expand.
Wireless LANs can be configured in a variety of ways. Can quickly expand from a small LAN with only a few users to a large network of thousands of users. And can provide between the nodes such as "roaming" and other characteristics of the limited network can not be realized.
Currently widely used wireless networks. The main wireless networking technologies include Bluetooth, LEE or 0211, and H0meRF.
This paper focuses on the lEEE80211 series of protocols based on the wireless local area network (WireIessLOcaIAreaNetworkWLAN) to introduce.
Second, the history and development of wireless LANs The historical origin of wireless LANs can be traced back to more than half a century ago during World War II, when the U.S. Army used radio signals for data transmission. They developed a set of radio transmission technology. They developed a radio transmission technology that used strong encryption, which was widely used by both the U.S. Army and the Allied Forces.
In 1971, researchers at the University of Hawaii created the first packet-based radio communications network, inspired by the technology used by the US Army during World War II.
This network, called ALOHNET . It consisted of seven computers in a bi-directional star topology that spanned four Hawaiian islands, with a central computer placed on the island of Oahu.
It can be called the granddaddy of wireless LANs.
In 1985. The U.S. Federal Communications Commission (Fcc) authorized ordinary users to use the "Industrial, Scientific, and Medical" (IsM) band. This led to the commercialization of wireless LANs.
IsM operates between 902MHz and 585GHz.
This operating band is just above the cellular band.
The JsM band provides a product band for wireless network equipment vendors, and end-users can use the equipment directly without applying to the Fcc.
The lsM band has had a tremendous positive impact on the wireless industry, ensuring the smooth development of wireless LAN components.
With the development of wireless LANs. The urgency of the establishment of various related specifications has become more and more prominent. 1990s. As a globally recognized authority on LANs, the IEEE802 Working Group has successively established a set of wireless LAN specification standards expressed in the form of protocols. And has been widely recognized and applied.
These protocols include the 8023 Ethernet protocol, the 8025 Token Ring protocol, and the 80232100BAsE-T Fast Ethernet protocol.
IWE released the first internationally recognized protocol for wireless LANs, the 80211 protocol, in 1997.
In September 1999, IEEE proposed the 80211b protocol. It was used to supplement the 80211 protocol, followed by a series of protocols such as 80211a, 80211g, and so on, thus further improving the specification of wireless LANs.
The specific protocols developed by the lEEE 80211 working group are as follows: (1) 802.11a: 80211a uses orthogonal frequency division (0FDM) technology to modulate the data. Using the 5GHz band.
0FDM technology divides the wireless channel into sub-frequencies that are transmitted in parallel at low data rates. These frequencies are then put back together at the receiving end. It provides a 25 Mbit/s wireless ATM interface and a 10 Mbit/s Ethernet wireless frame structure interface as well as an air interface for TDD/T[)MA.
To a large extent, it can increase transmission speed and improve signal quality. Overcoming interference.
The physical layer rate is up to 54Mblt/s, and the transport layer is up to 25Mblt/s. It can satisfy both indoor and outdoor applications.
(2) 802.11b: 80211b is also known as Wi-FJ technology